Telemetric indicating system



Dec. 16, 1947. w, p, A 2,432,772

TELEMETRIC INDICATING SYSTEM Original Filed Aug. 12, 1942 INVENTOR. W/LL ///M F. Li/H? ATTORNEY TELEMETRIC INDICATIN G SYSTEM William P. Ilear, North Hollywood, Calif., assignor,

by mesne assignments, to Lear, Incorporated, .Grand Rapids, Mich., a corporation of Illinois Original application August 12, 1942, SerialNo.

Patented Dec-. 16', 1947 454,559. Divided and this application January 15, 1944, Serial No. 518,467

2 Claims. (Cl. 177-351) 1 This invention relates to self-orlenting-remote indicators, particularly for use aboard aircraft to afford a plurality of remote indications of the readings of a master instrument. This applicavention. The system is energized by a local alter hating current source l3 that is aboard the aircraft. A 400 cycle supply is indicated. The directional gyroscope I is of the conventional type, comprising a rotor I! mounted with three degrees tion is a division of my cop pp t o 5 offreedom. The gyroscope rotor I! may be Serial No. 454,559, filed August 12, 1942 for Comelectrically or pneumatically driven, as will be p n l sy n w Pat n N 2,403, 9 understood by those skilled in the art. Gyro dated July 2, 1946, and assigned to the same rot-or I1 is spun about a horizontal spinning axis assignee as this case. a supported in gimbal ring I 8, which in turn is Large modern militaryaircraft generally re- 10 freely mounted on bearings I9 in vertical ring quire, throughout the aircraft, a number of re- 20. Vertical ring 20 is rotatably supported about mote indications of the readings of master ina vertical axis on suitable bearings in the gyrostruments so that the co-pilot, navigator, bomscope. bardier and others thereon, may have continuous Conventional auxiliary means for driving and indication of various data necessary to the proper caging the gyroscope, not shown, are to be d performance of their duties. Systems of the stood as incorporated in the schematically repreprior art provide only a limited number of remote sented directional gyroscope l0. Directional gyroindications. An important aspect of the system scope I0 is of standard size and design, being ad- 'Of my present invention is the provision of any ditionally provided with a precession correction number of remote indicators. These indicators winding mounted within the gyroscope. Wi de a at y locally generat d electronic ing 25 is concentric about horizontal gimbal ring t l u s y ar i ni and o r is. A bearing pick-oil unit 26 is supported on spond in position with the master instrument a late that i mounted on top of the gyroscope With Which t y are operatively as ate casing. Unit 26 comprises a central vertical m i di t r f e p s i v n n r p 25 shaft 28 which is secured to vertical ring 20 of the ticularly useful in compass directional systems gyrgscope Practically no torqu or force is of the ype in in a m n co p an a parted to the gyroscope by unit 26, as will herer i n lyr p o vely upled toinafter be set forth in more detail. The direct With t m t indicators'of the Present tional position of the gyroscope is in this manner invention, continuous accurate indications of any directly communicated to ick-01f unit 26. The given data are simultaneously provided throughpractically torqueless o-r energyless pick-ofi of t t e aircraft, Without loading Otherwise signal indications from master instruments is an fleeting errors back on to the master instruments. important feature of the present invention, as These a further advantages, O j a this type of pick-ofi prevents loading errors of Capabilities o my present invention will become the remote indicators from being reflected back more pp t in e follo g description of onto the master instrument. Thereby, the acp f r d embodiments h f. sh wn in h a curacy of indication of the master instrument is pa y d w s, in which: not, impaired irrespective of how many remote in- 1 is a schema el ctri al diagram f one dicators are electronically coupled therewith. embodiment which my invention may assume in Unit 26 corresponds to a transmitter component p of a self -synchronous type telemetering arrange- Fig. 2 is a diagrammatic representation of the merit, and is energized by the local alternating self-aligning remote indicator a ge t o current source it through lead 29 and the ground the invention. connection indicated. Pick-off unit 26 is inter- Fig. 3 is aview in elevation, partially in section, connected through cable 3| with a correspo of one form which the remote indicator of the ing pick-oii unit 30 that is coupled to magnetic invention y a e in Practice compass H. A control si nal is derived from the The remote indicators of the present invention interaction of pick-off units 26 and 30. The cona of ene a application a d may be used in trol signal is introduced into the directional conny y m where a plurali y f r mot i icatrol unit, l2 by lead 32 and common ground cont ons o the readi s of e o m e mast nection. A uni-directional control current is struments are required. For illustrative purgenerated at the output of electronic unit i2. and poses, the indicators will be described as inconected by leads 33 to precession correction coil o pora ted in the Co p system of my a 25. A uni-directional corrective flux is produced identified patent. As shown in Fig. 1, such sysby coil 25 that reacts with permanent magnets term includes a directional gyroscope Ill, magnetic 35, 35 ecured t horizontal gimbal ring l8. The compass l'l, intercouplcd electronic directional corrective force thus exerted on magnets 35 is in control unit I2 and remote indicators 15, which a direction so as to counteract any precessional latter are the subject matter of the present inor turning errors that the gyroscope may tend to incur, In this manner the orientation and indifollows.

the earth's magnetic field. The directional'orientations of the magnetic bar are communicated to the inductive electrical pick-off unit 88, as A small magnet 42 is mounted at the upper end of spindle 38. A second magnet 48 is mounted above magnet element 42 and serves as a follow-up or slave magnet. Magnet 48 is connected to the rotor of pick-off unit 80 through shaft 44. Thus the azimuthal bearing indications of the main compass bar are faithfully communicated to the rotor of pick-off unit 38. Such action is with the application of negligible drag or torque which might interfere with accurate directional alignment of the compass magnet bar.

By my system, any number of remote bearing indicators may be incorporated without introducing drag on either of the position determining units, in this case compasses i8 and II, since the indicators are locally energized and selfaligning, as will be set forth in more detail hereinafter. The compass pick-off units 28 and 30 are such as are generally known and used in the art of telemetering such as Selsyns." They comprise symmetrical rotor and stator components, interconnected so as to derive a stabilized electrical current and magnetic flux relationship therebetween. The stators are multi-phase wound, e. g. three-phase. The illustrated units 28, 38 have three-phase delta connected stator windings 45, 41 and single-phase rotor windings Corresponding terminals of the three-phase stators 45 and 4'! are interconnected by the three wire cable 3 I. The local alternating current supply l8, which in modern aircraft is usually at 400 cycles, is connected by lead 28 to the single phase rotor coil 46 of pick-off unit 28. As described above, rotor 48 is mechanically coupled to vertical ring 20 of gyroscope l8 through shaft 28. Rotor winding 48 of pick-off unit 38 is electrically connected by lead 32 to the input of electronic unit i2. Rotor 48 also is mechanically connected by shaft 44 to slave magnet 43 of the magnetic com pass I I, as previously described.

The single-phase voltage applied to rotor 48 produces a sinusoidal magnetic field that induces voltages in the three-phase stator winding 45. The relative phase and magnitudes of the voltages induced in the three component branches of stator 45 depend upon the angular position of rotor 46 within the stator. Such angular position of rotor 46 is in turn controlled by the directional orientation of the gyroscope I0 through vertical ring 20. The induced voltages appearing at the terminalsof stator 45 are transmitted to the corresponding terminals of stator 41 to produce currents in the windings of stator 41 that correspond with those in winding 45. A magnetic field is thereby set up within stator 41 that is identical in space and time phase relationship with the field within stator 45 as generated by rotor 46. The flux within stator 41 is sinusoidal in time. This flux induces a corresponding sinusoidal voltage in rotor winding 48 of unit 38.

The magnitude and phase of the voltage produced across coil 48 by stator 41 depend upon the angular space phase of coil 48 within stator 41. The induced voltage action is similar to that of a directional loop antenna responsive to a radio signal. The induced voltage is characterized by a flgure-of-eight pick-up pattern. The phase of the resultant voltage in coil 48 is in-phase or out-of-phase with the magnetic flux of stator 41. The magnitude of the voltage across rotor 48 is proportional to the sine of the angle which coil 48 makes with its zero pick-up position in the flux in stator 41. The rotor 48 induced voltage is impressed upon the control electrode of electronic amplifier tube 50 in unit l2. The voltage from rotor coil 48 constitutes a control signal for the system. The control signal is amplified in a conventional manner by triode 50, and impressed upon the control electrodes of a pushpull amplifier stage 5 I, 52 through transformer 53.

The control signal provided by the rotor 48 is of a magnitude that is directly dependent upon the angular difference that exists between bearings of the directional gyroscope I0 and magnetic compass i I, and of phase that is directly dependent upon the sense of the angular dlflerences.

The reason is that the space phase of the sinusoidally varying magnetic field within stator 41 depends upon the angular position of rotor coil 48 within its stator 45. The space phase of the flux within stator 41 is thus directly controlled by the angular bearing position'in azimuth of directional gyroscope I0. 0n the other hand, the angular position of rotor coil 48 within stator 41 is determined by the angular bearing position of the magnet bar of the magnetic compass II. Accordingly, the sinusoidal voltage impressed upon rotor coil 48 is determined by the spatial angular difference in azimuth existing between the two compasses III, II. The larger such angular difference, the greater the magnitude of the induced control voltage from coil 48 impressed upon electronic unit I 2.

The control action is on the directional gyroscope I0 in a manner such as to bring it in line or tie in with the average magnetic compass north position. Such action is automatic and continuous in the system, and accordingly no substantial angular discrepancy can exist between the bearing indications of the compasses, nor pull apart the relative spatial positions of rotor coils 46 and 48 for a sufficient length of time to throw the system out of synchronism. For this reason also, the possible 180 pick-up ambiguity of the rotor coil 48 signal cannot in practice interfere with the determined sense relationship that controls the gyroscope precession correction action.

The control voltage at coil 48 will thus in practice be within a practical operating range of values, and its sense determines the direction of the precessional control on gyroscope I8 through coil 25 as follows. The control voltage introduced by lead 32 to electronic control unit I 2 is impressed upon the grid electrodes of push-pull tubes 5|, 52 in opposed or 180 out-of-phase relationship by push-pull transformer 58. Anodes 54, 55 of tubes 5|, 52 are connected to alternating current source l6 by lead 58 through a center tap on precessional control coil 25. Thus the anodes of control tubes 5|, 52 have the local reference alternating current voltage continuously impressed thereon in phase.

The control tubes accordingly selectively respond to the control voltage corresponding to the signal from rotor 46. The phase of the control voltage impressed on unit l2 determines which of control tubes 5|, 52 is rendered conskilled in the art. The in-phase and sinusoidal character of the'anode voltage on tubes 5|, 52 permits only one of them to conduct in corre-- spondence with the phase of the control voltage applied to their grid electrodes. Thermionic tubes 5|, 52 may be vacuum or of the gaseous variety, such as the so-calle'd thyratron or trig- Ker control tubes. 5|, 52 are connected together and are suitably electrically biased by direct current voltage source 55.

A potentiometer E'I-a'cross bias voltage source forms a sensitivity control for the precessionalcorrecting action. 'Potentiometer 5! setting determines the relative magnitudes of the resultant imi-directional control current applied to coil ztdependent uponthe control signal magnitudes. The phase of the control signal voltage impressed upon the grid electrodes of either tube 5| or 52 is either in-phase or 180 out-ofphase with respect to the reference phase of the local A. 0. It as applied to the anodes thereof. The control tube wherein both the impressed control voltagezand anode voltage are in-phase render that tube conductive to produce a corresponding uni-directional current flowing through its associated section of the precession coil 25,

The direction of flow of the control current impressed upon either half of winding. 25 is predetermined to react on permanent magnet elements 35, 35, and thus on gyroscope gimbal ring l8, in amanner to counteract or otherwise negative the bearing discrepancy which the gyroscope may tend to assume with respect to the magnetic compass. In other words, any angular discrepancy of the gyroscope which begins to arise due to northerly turning error, precessional error, or the like, causes an angular differential between rotors 46 and 48, which correspondingly produces the control signal at rotor 48 as previously set forth. The phase of the control signal is determined by the. sense of such angular discrepancy, which phase is pre-relatecl to the circuital connections of control tubes 5|, 52 and the associated precession control coil 25, as well as the physical disposition of magnets 35, 35 on the gyroscope, in a manner to return the gyroscope orientation back to the angular position corresponding to the true magnetic north position of the magnetic compass. The sensitivity control of the precession action is adjustable by potentiometer 51, and in practice the overall action is determined by suitable physical design of the system components. It is thus unnecessary to periodically readjust the directional gyroscope for precessional errors, since such are auto: matically eliminated by reference to and control by the average northerly readings of the magnetic compass l.

The present invention relates to remote selfpowered indicators with which sufllcient control signal to operate the same is obtained from stator signals from the unit 26 coupled to directional gyroscope III, or to any other master instrument. The particular source of the control signal may be the result of an automatically positioned yroscope as illustrated in the present drawings, or any other displaceable device, or it may be a manual preset control mechanism.

The remote indicator units l5 are electrically connected to the compass system in a manner to avoid interference with the normal bearing indications of both compasses. Any number of The cathodes of the tubes within the stator.

of the longitudinal aircraft axis with respect to the true magnetic north. Indicators I5 are selforientating, deriving their energization from the local alternating current source I6. Each indl-' cator unit I5 comprises an electronic motor driven component 52, and a stator-rotor unit 63, 64

coupled thereto by a shaft 65. The stator-rotor I units 63, 64 of indicators |5 are similar in design with the corresponding telemetering stator-rotor units 26 and 30 coupled to compasses H), II. Three-phase delta wound stators 63 are connected to three-wire cable 3|, in correspondence with the connections of the main stator units 26, 3!]. Control units 62 of indicators l5 are energized from local alternating current source I6, through lead 66, and ground, i

The self-orienting remote indicator of the invention, schematicaly indicated at I5, is diagrammatically illustrated in Fig. 2. The unbalanced voltages produced by gyroscope piok-ofi. unit 26 and introduced into three-wire cable 3|, are correspondingly impressed upon the three-phase stators 53 of indicators l5 connected therewith. These voltages set up currents in the windings of stator 53, producing a magnetic flux condition Such flux corresponds to that resulting in stator 41. The rotor 64 within stator 63 thus has a voltage induced therein of magnitude and phase corresponding to the-angular position of rotor 64.with respect to that of gyroscope rotor unit 46. The reasons for this action are the same as hereinbefore described in connection with the signal voltage induced in rotor 48 by stator 47. The sense of the voltage induced in rotor 64 will accordingly be in-phase or 180 out-of-phase with respect to the local alternating current. source l5, and of magnitude depending upon the ofi-angular position of the rotor coil 64. The true or null angular position of soil 64 will always correspond to the angular position of the directional compass bearings, at which position zero voltage is impressed upon the rotor 64.

Rotor B4 of remote indicator I5 is directly coupled by shaft 65 to indicator pointer 60. Shaft 65 is coupled to the rotor 19 of the control motor by reduction gearing 8| through shaft 82. Indicator control motor 80 is shown of the splitphase or two-phase alternating current type, 10- cally energized by alternating current source it and controlled by the voltage signal generated at rotor coil 64 as follows. The terminals of rotor coil 54 are respectively connected to control electrodes B3, 84 of a pair of thermionic tubes 85, 86. Tubes 85, 86 may be contained in a single envelope. The cathodes of tubes 85, 86 are connected to ground through biasing resistors 81,88. Tubes 85, 86 may. for example, be biased for either class A or class B operation. The anodes 89, 90 of motor control tubes 85, 86 are connected to individual. oppositely phased, stator windings 9|, 92 of motor 80. A third winding 93 of motor 80, arranged 90 out of space phase with the windings 9|, 92, as in the usual design of a splitphase motor, is connected to the local alternating current source I 6 through a substantial starting capacitor 94.

When pointer 60 is at -its proper directional position, a zero signal voltage obtains across the terminals of rotor coils 64, and no current flows through tubes 85, 86 or motor stator windings 9|, 92. Motor 80 is accordingly at rest and pointer 60 remains at its proper indicating position. When the angular attitude of the aircraft changes, this moves the casings of directional gyroscope l and magnetic compass l I about their directionally stable elements, which produces a correspondingly changed bearing indication of the compasses with respect to their indices or lubber lines. Similarly, the rotors 46 and 48 being physically coupled to the spatially orientated compass elements 20 and 39, are rotated within their associated stator coils 45 and 47. This action causes a changed distribution in the unbalanced voltages within cable 3|.

The voltage and magnetic flux redistribution occurs simultaneously at allthe stator elements, including stators 45,

of the stator voltages and flux occurs, a corresponding voltage is set up within indicator rotor coils 64, the phase of which depends upon the sense of the angular change. The control electrodes 83, 84 of motor control tubes 85, 86 thus have a voltage applied that is pre-related to the fixed reference voltage on their anodes 89, 90 from the local A. C. source Hi. This action causes a preponderance of alternating current at the local frequency in one of the two motor stator windings 9|, 92. Rotor 19 of motor 80 is accordingly rotated in the direction to cause rotor coil 64 to follow the changing orientation of the stator 63 flux.

The direction of rotation of rotor coil 64 is such that it follows its zero voltage pick-up relation with the surrounding stator flux. Since pointer 60 is connected to rotor coil 64, it is correctly carried to the new angular position which the compasses I0, I I assume with respect to the aircraft attitude. When a stable compass hearing position is'reached, the zero voltage pick-up position prevails, and motor 80 promptly stops. The reduction gearing 8| facilitates precise stoppage, and inhibits hunting. A similar action prevails when a discrepancy arises or tends to arise between the bearing indications of the directional gyroscope In with respect to those of the mag-' netic compass. In the latter instance, the stator winding flux distribution is temporarily orientated to bring both compasses into correspondence, in the manner previously described, and the stator-rotor 63, .64 reaction thereto is the same. The remote indicator pointers 60 will accordingly always be oriented in the stable compass azimuthal bearing position with respect to their associated cards 6 I. The remote indicator unit I5 is fully energized from the local A. C. source, and does not produce a drag on the main compass units.

Fig. 3 is an elevational view, partly in section, of a physical form which self-orientating indicator I 5 may assume. The indicator 15 shown in Fig. 3 incorporates ah the components indicated in schematic diagram, Fig. 2. The pointer 60 and card 6| are at the top, and are viewed through transparent pane 95. The stator and rotor coils 63, 64 are arranged with the pointer 60 within a shoulder 96 extending from the indicator housing 91. Shaft 65 projects from rotor 47, and stators 63 of each of' the remote indicators l5. As this redistribution 64 into housing 91 and is coupled to reduction gearing 8|. Reduction gearing BI is supported on a shelf 98, and is shown connected to rotor 79 of motor 80. Rotor 19 is of. the drag-cup type. Control tubes 85, 96, condenser 94, and the-other electrical elements and connections of indicator l5 are also incorporated within the housing 91'.

The resultant arrangement is compact, light in weight, rugged, and fool-proof. Such selforienting units may be used to readily provide compass indications and in any number of remote points aboard the aircraft.

Although I have described a preferred embodiment for carrying out the principles of my present invention, it is to be understood that modifications thereof may be made by those skilled in the art without departing from the broader and scope of the invention a deflned in' system comprising an a multiphase winding,

with respect to its stator, said indicator stator being substantially ineffective to affect the distribution of voltages in the closed system by reflecting errors to said controlling stator.

2. A remote indicator system comprising an indicator stator having a multiphase winding, a closed circuit including said stator and a multiphase wound controlling stator, an indicator rotor winding inductively coupled with said indicator stator, an index element, a common shaft for said rotor winding and element, a locally en,- ergized reversible electric motor having a 'normally energized field winding, a pair of oppositely phased field windings, and a, rotor coupled with said shaft through reduction gearing, electronic means responsive to current induced in said indicator rotorwinding one of said pair of field windings of said motor until said indicator rotor achieves electrical equilibrium with respect to its stator, said indicator stator being substantially ineffective to affect the distribution of voltages in the closed system by reflecting errors to said controlling stator.

WILLIAM P. LEAR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,547,435 Mittag July 28, 1925 2,203,478 Wills June 4, 1940 2,331,934 Satterlee Oct. 19, 1943 1,743,794 Murphy Jan. 14, 1930 2,364,450 Keeler Dec. 5, 1944 FOREIGN PATENTS Number Country Date 280,682 Italy Dec. 17, 1930 for selectively energizing for selectively energizing Certificate of Correction Patent No. 2,432,772. December 16, 1947.

WILLIAM P. LEAR It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Column 4, line 73, for f rotor 46 read rotor 48; column 6, line 51, for soil 64 read coil 64; and that the said Letters Patent should be-read with these corrections theerein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 6th day of April, A. D. 1948.

THOMAS F. MURPHY,

Assistant Uommz'ssz'oner of Patents. 

